[Hondor]

It's not forbidden, it just has a ~10% tariff (fine). $10 per MWh compared to the current price of $120 per MWh. If solar or wind ends up actually cheaper than coal, it'll probably be by more than that 10% so it'll still be economical to use them.

Furthermore, the fine doesn't apply to exported electricity, which is most of it: "Wyoming sends two-thirds of the electricity it generates to nearby states" [1]

[1] https://www.eia.gov/state/analysis.cfm?sid=WY

[philipkglass]

$120 per MWh (well, $115.60) is the residential retail price in Wyoming, not the price that electricity producers get at point of generation:

https://www.eia.gov/electricity/monthly/epm_table_grapher.cf...

The wholesale price a new American wind farm gets for its output in a region with good resources is maybe $30-$40/MWh. (Or $40-$50 if the wind farm lasts 25 years and collects the federal Production Tax Credit for its first 10 years.) The extra $10 in taxes makes a bigger difference at the wholesale level.